Microdispensing pumps are known in the prior art, such as those disclosed in U.S. Pat. No. 5,152,435, which issued Oct. 6, 1992; U.S. Pat. No. 5,881,956, which issued Mar. 16, 1999; and WIPO Published Patent Application No. WO 01/14245. The disclosures of these references are incorporated by reference herein in their respective entireties.
Although microdispensing pumps are known in the prior art, because of the minute doses of the pumps (5-15 microliters), microdispensing pumps have problems associated therewith not found with pumps used for larger dosages. For example, fluid residing within, or adjacent to, a nozzle may evaporate between doses, thereby altering the volume of a next-administered dose. With relatively large doses, typically in the range of 80-100 microliters, evaporation of such fluid is generally inconsequential in maintaining required dosage amounts. However, such evaporation may have an effect on microdoses.
Additionally, internal components of a microdispensing pump define a fluid passageway which requires relatively tight tolerances. Easier compliance with manufacturing stringency is desired with microdispensing pumps.